(1) Field of the Invention
This invention relates to a process for improving the radiation resistance of cellulosic fabrics.
(2) Description of the Prior Art
Phenyl esters and benzyl type ethers of cellulose have been used to improve the radiation resistance of cellulosic fabrics. The phenyl esters are prepared by reaction of sodium cellulose with ##STR1## acid chloride to form the corresponding cellulose benzoates. The other reaction that is commonly employed involves the reaction of benzyl chlorides with sodium cellulose to form benzyl ethers of cellulose. The resultant fabrics show ##STR2## improved strength retention when exposed to radiation. Other compounds have been used to achieve the same effect but the reaction involves either the use of an acid chloride as in the case of cinnamyl chloride or naphthoyl chloride ##STR3## or more complex benzyl type chlorides such as benzhydryl or trityl chlorides.
The use of these agents for reaction with cellulose to produce radiation resistant cellulose poses several difficulties. First, acid chlorides and benzyl chlorides are lachrymatory and handling them requires closed systems. Second, they are not water soluble, so reactions are heterogeneous and large excesses of reagents are required. Third, in order to achieve the high degree of substitution required with these reagents reaction times of up to 6 hours or more are required.
Although benzoylation can be speeded up by the use of pyridine as the solvent, as described in U.S. Pat. No. 3,519,382; there is still the limitation of handling an acid chloride in a malodorous solvent.
Finally, some comment should be made relative to the high degree of substitution (DS) required of the agents described in the prior art. While DS varying from 0.3 to 1.5 are reported it is apparent that a DS of 0.5 is required [J. of Applied Polymer Science 11, 1129-1138 (1967)] to achieve maximum strength retention after irradiation.